Johnson Matthey has won approval from the US Environmental Protection Agency (EPA) for its new diesel oxidation catalyst (DOC) for use in on-road engines.

The ruling covers models built in the years from 1991 to 2003, and will mean that Johnson Matthey can sell the catalysts under its trade names CEM and DCC.

The DOCs have been approved for use with diesel fuels that come under the 500 ppm sulphur content.

JM says the platinum-based catalyst is "ideal for use in areas that do not yet have access to ultra low sulphur diesel (ULSD) fuel".

"Diesel engines are renowned for their durability, lasting hundreds of thousands of miles often for several decades per engine. This verification extension now covers more of the older, higher polluting diesel engines that will remain in use for many years to come," the firm stated.

In conjunction with the catalyst, the DOCs use a proprietary component to minimise sulphate formation during operation with regular, on-road sulphur fuel.

When used in conjunction with a ULSD fuel conversion, the combined application boasts a 30 per cent particulate matter reduction over the original engine standards.